Generally known is a printer of a type such that a paper roll is placed on a receiving portion of a paper roll holder and a paper sheet paid out from the paper roll is printed. In this printer, the paper roll rotates on the receiving portion as the paper sheet is paid out from the paper roll.
In the printer of this type, a shortage of the residual quantity of the paper roll is detected by utilizing a reduction of the radius of the paper roll and lowering (or movement toward the receiving portion) of the position of its roll core (see Japanese Patent Application Laid-Open No. 4-176674).
If the paper roll is lightened in weight with its residual quantity lessened, however, the paper roll tends to jump up from the receiving portion or roll on the receiving portion, urged by a force that is generated when the paper sheet is paid out from the paper roll. Thereupon, the position of the paper roll varies, so that the residual quantity of the paper roll cannot be detected. If the paper roll lifts off the receiving portion, moreover, fixed-rate feed to a printing section may be destabilized or noise may be generated, in some cases.
In order to prevent the paper roll from lifting off the receiving portion, therefore, there is proposed a method in which the paper roll that is placed on the receiving portion of the paper roll holder is pressed down with a spring-urged pressure member from above (see Japanese Patent Applications Laid-Opens Nos. 58-22245 and 4-176674).
However, the printer having the pressure member constructed in this manner requires a mechanism for retreating the pressure member from a path of movement of the paper roll toward the receiving portion lest the pressure member hinder the paper roll from being loaded into the paper roll holder.